Mono- or polyamide compounds containing an amino group having active hydrogen have hitherto been used as hardening agents for epoxy resins. Most of these compounds are obtained by reacting at least one carboxylic acid selected from polymerized fatty acids and carboxylic acids with a polyalkylenepolyamine, and are called polyamide-type hardening agents or polyamideamine-type hardening agents. These hardening agents have many advantages, for example, they can be used at various proportions to epoxy resins, as well as they have long pot-life, low toxicity as compared with amine type hardening agents, excellent flexibility and adhesiveness of the hardened product obtained from these hardening agents and epoxy resins, and so on. On the other hand, these hardening agents are disadvantageous in that they show poor compatibility with epoxy resins and that the hardened products, when hardened at ambient temperature, have insufficient transparency, strength and chemical-resistance, etc. Further, in some cases, an aging time would be required for obtaining good hardened epoxy resin products, thus giving rise to a problem of reduction in working efficiency.